Effects of Incentives vs Normative Feedback on Bio-waste Sorting in the Field

Last registered on February 09, 2024

Pre-Trial

Trial Information

General Information

Title
Effects of Incentives vs Normative Feedback on Bio-waste Sorting in the Field
RCT ID
AEARCTR-0010600
Initial registration date
October 17, 2023

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
October 17, 2023, 2:43 PM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
February 09, 2024, 4:28 AM EST

Last updated is the most recent time when changes to the trial's registration were published.

Locations

Region

Primary Investigator

Affiliation
Universidad Pública de Navarra

Other Primary Investigator(s)

PI Affiliation
Universitat de les Illes Balears
PI Affiliation
Toulouse School of Economics
PI Affiliation
Toulouse School of Economics

Additional Trial Information

Status
In development
Start date
2023-02-27
End date
2025-02-01
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
This RCT consists of a field experiment about bio-waste recycling in the city of Palma (Spain). Citizens of Palma must scan a card that identifies them in order to use the bins meant for bio-waste sorting. Such bins are available on streets throughout the city, next to the bins for recycling of glass, plastic, and paper. The city's waste management company will provide the research team with data on the bio-waste sorting behaviors of the households who signed up to participate in the study, both prior to the treatment and for several months after the treatment (at least until July 2024). The goal is to study how the participants' use of the bio-waste sorting bins is affected by intrinsic (Kantian) and extrinsic (incentives) motives. The participants will be allocated to one of three treatments. Each subject will receive one text message from us, at some point between February 10 and February 24.

Note: The initial plan was to send messages via Whatsapp in October 2023, and we did send messages to 400 subjects. However, a large enough number of them reported us as spam, implying that we could not send any more messages. This forced us to edit the design (with Whatsapp we could send images; now that we must use SMS instead, we can only send simple text messages). In the current study, these 400 households are dropped from the subject pool.
External Link(s)

Registration Citation

Citation
Alger, Ingela et al. 2024. "Effects of Incentives vs Normative Feedback on Bio-waste Sorting in the Field." AEA RCT Registry. February 09. https://doi.org/10.1257/rct.10600-2.0
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Experimental Details

Interventions

Intervention(s)
INTRODUCTION: The treatment and randomization unit in the study will be households located in the areas of the city of Palma (Spain) where individuals must use a personal card to use the bins meant for bio-waste sorting. Hence, each bin use is recorded and associated with one household, allowing us to track the participating households' use of the bio-waste sorting bins.

RECRUITMENT: Participants were recruited first between the 27th of February 2023 and the 30th of June; a second recruitment took place between 30th November 2023 and 25th January 2024. Recruitment was carried out face-to-face by directly approaching people in the street, by the internet through advertisements in social media, and by placing flyers in the city. The participants were informed that the study would be about bio-waste sorting behavior and that they would receive messages by WhatsApp or SMS; in the first round recruitment was facilitated by offering those who signed up to win one of four prizes of €250 each (only one individual per household could sign up). The certified random draw of the winners was performed by the independent firm "Easypromos" on the 27th of July. Each participant signed an informed consent form and answered a questionnaire that collected basic demographic data (number and ages of people in the participant's household, annual income, contact information, …) as well as data on social norms, personal norms, and relationship with nature (beliefs about average environmental sensitivity in the population, motivations to recycle, ...). Among those who signed up, only residents of Palma living in a neighborhood with the new electronic bio-waste sorting bins, in possession of the card required to open the bio-waste sorting bins, and who provided a valid cell phone number were included in the final sample.
Intervention (Hidden)
ALLOCATION TO TREATMENTS:
The 1,329 participants were divided into three groups of equal size. The three groups are balanced in terms of the recruitment process.

INTERVENTION:
We let the sample rest until February 9th, 2024. Pre-intervention data (at least 20 weeks) will be used for balancing tests.

The intervention consists of sending one text message to each participant. In each group half of the participants will receive the message on February 10th 2024, while the other half will receive the message on February 24th 2024. In between the two sending periods, the group that receives the message later (on February 24th) will be used as a control to quantify the effect of receiving a message.

All the participants receive the following message, and this is the only message that the control group receives:

"Thanks for participating in this study on bio-waste recycling conducted by Universitat de les Iles Balears. Did you know that each week that a citizen of Palma recycles their bio-waste, they reduce, approximately, CO2 emissions by the same amount as a tree absorbs in 17 days?"

Note: in the statement "Did you know that each week that a citizen of Palma recycles their bio-waste, they reduce, approximately, CO2 emissions by the same amount as a tree absorbs in 17 days?", the number 17 was calculated based on past bio-waste sorting data provided to us by the waste management company Emaya.

The participants in the "incentives treatment" also receive the following text:
"Recycling has a prize this fortnight! For each week that someone in your household uses a bio-waste recycling bin between 02/12/2024 [02/26/2024] and 02/25/2024 [03/10/2024] (both inclusive), you will obtain one chance to win one out of five prizes of 280 euros"

The participants in the "Kantian treatment" also receive the following text:
"Imagine by how much CO2 emissions would be reduced if your household recycled its biowaste and all the other households in Palma also did the same as yours!"



TIME HORIZON OF THE STUDY:
To evaluate the effects of the intervention in the medium-long term, we will wait for a minimum of 3 months to start running the analysis.

OTHER INFO/COMMENTS:
1. The last week of February and the first of March 2023, we conducted a lab-experiment designed to test the effects of several messages. This lab-experiment was used to tailor the field intervention.
2. If feasible, after the intervention (in June or July 2024), we will run a post-intervention survey to collect information about the mechanisms at work.
Intervention Start Date
2024-02-10
Intervention End Date
2024-03-11

Primary Outcomes

Primary Outcomes (end points)
Dummy variable that indicates for each week whether the household used the bio-waste sorting bin (1) or not (0)
Proportion of weeks that each household uses the bio-waste sorting bin at least once.
Primary Outcomes (explanation)
"Proportion of weeks that each household uses the bio-waste sorting bin at least once in each week" is computed by aggregating the "Dummy variable", indicating for each week whether the household used the bio-waste sorting bin (1) or not (0), over households and weeks.
This measure provides us with a measure of the average proportion of weeks that households recycled during the studied period which captures systematic recycling participation.

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
This RCT consists of a field experiment about bio-waste recycling in the city of Palma (Spain). Citizens of Palma must scan a card that identifies them in order to use the bins meant for bio-waste sorting. Such bins are available on streets throughout the city, next to the bins for recycling of glass, plastic, and paper. The city's waste management company will provide the research team with data on the bio-waste sorting behaviors of the 1,329 households who signed up to participate in the study between 27th February and 30th June 2023, and between 30th November 2023 and 25th January 2024. The goal is to study how the participants' use of the bio-waste sorting bins is affected by intrinsic (Kantian) and extrinsic (incentives) motives. The participants will be allocated to one of three treatments in two different waves.
Experimental Design Details
ALLOCATION TO TREATMENTS:
The 1,329 participants were divided into three groups of equal size. The three groups are balanced in terms of the recruitment process.

INTERVENTION:
We let the sample rest until February 9th, 2024.

The intervention consists of sending one text message to each participant. In each group half of the participants will receive the message on February 10th 2024, while the other half will receive the message on February 24th 2024. In between the two sending dates, the group that receives the message later (on February 24th) will be used to quantify the effect of receiving a message.

All the participants receive the following message, and this is the only message that the control group receives:

"Thanks for participating in this study on bio-waste recycling conducted by Universitat de les Iles Balears. Did you know that each week that a citizen of Palma recycles their bio-waste, they reduce, approximately, CO2 emissions by the same amount as a tree absorbs in 17 days?"

Note: in the statement "Did you know that each week that a citizen of Palma recycles their bio-waste, they reduce, approximately, CO2 emissions by the same amount as a tree absorbs in 17 days?", the number 17 was calculated based on past bio-waste sorting data provided to us by the waste management company Emaya combined with the CO2 emission equivalences provided by Fan et al. (2020a,b) and the European Environment Agency (2016)

The participants in the "incentives treatment" also receive the following text:
"Recycling has a prize this fortnight! For each week that someone in your household uses a bio-waste recycling bin between 02/12/2024 [02/26/2024] and 02/25/2024 [03/10/2024] (both inclusive), you will obtain one chance to win one out of five prizes of 280 euros"

The participants in the "Kantian treatment" also receive the following text:
"Imagine by how much CO2 emissions would be reduced if your household recycled its biowaste and all the other households in Palma also did the same as yours!"

All the participants receive a closing message with a link providing information about the study. The platform used for sending the messages can track the participants who clicked the link.

TIME HORIZON OF THE STUDY:
To evaluate the effects of the intervention in the medium-long term, we will wait for a minimum of 3 months to start running the analysis.

OTHER INFO/COMMENTS:
1. The last week of February and the first of March 2023, we conducted a lab-experiment designed to test the effects of several messages. This lab-experiment was used to tailor the field intervention.
2. If feasible, after the intervention (in June or July 2024), we will run a post-intervention survey to collect information about the mechanisms at work.



REFERENCES:
Van Fan, Y., Nevrlýb, V., Šompláka, R., & Smejkalováb, V. (2020). The Potential of Carbon Emission Footprint Reduction from Biowaste in Mixed Municipal Solid Waste: EU-27. Chemical Engineering, 81.
Van Fan, Y., Klemeš, J. J., Walmsley, T. G., & Bertók, B. (2020). Implementing Circular Economy in municipal solid waste treatment system using P-graph. Science of The Total Environment, 701, 134652.
European Environment Agency (2016) EEA Report No 5/2016 (2016). European forest
ecosystems. State and trends. Luxembourg.







Randomization Method
Household level randomized by a computer. The assignment to the treatment arm is done through the "randtreat" command in Stata stratifying by recruitment source (Form, Twitter, street, 2nd recruitment wave) using setseed(51). The assignment to the "texting wave" is done through the "randtreat" command in Stata stratifying by treatment and recruitment source (Form, Twitter, street, 2nd recruitment wave) using setseed(2)
Randomization Unit
The randomization unit is the household.
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
1,329 households.
Sample size: planned number of observations
Weekly behavior of the 1,329 households.
Sample size (or number of clusters) by treatment arms
443 households per treatment arm.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
According to pre-intervention data, the average household in our study uses bio-waste sorting bins with a weekly frequency of 0.1876207, showing a standard deviation of 0.324002. For a power analysis of 80%, given the sample size we intend to have, we guarantee, at least, a minimum detectable effect of 0.0610 in the use frequency at 95% confidence and 0.0745 at 99% confidence.
Supporting Documents and Materials

Documents

Document Name
IRB aproval
Document Type
irb_protocol
Document Description
File
IRB aproval

MD5: 4b11d6030a966fecb3e31b329cf0d3c8

SHA1: bfc0428f0f1a3c2099411ae7ad7941c1805b2b91

Uploaded At: October 17, 2023

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IRB

Institutional Review Boards (IRBs)

IRB Name
Comitè d'Ètica de la Recerca
IRB Approval Date
2022-09-05
IRB Approval Number
287CER22

Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
No
Data Collection Complete
Data Publication

Data Publication

Is public data available?
No

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials